Considerations for Developing Regulatory Guide for the Accident Analyses Employing Advanced Safety Features

For the regulatory safety review of the new design features, it is important to develop a regulatory guide considering the design and operating characteristics of the new design features. Beneficial as well as adverse effects on the safety should be identified and verified. Korea Institute of Nuclear Safety(KINS) has been evaluating the effects of these advanced safety features on the safety since 2012. As a result, KINS has been developing regulatory guide for the accident analyses employing the advanced safety features through the long-term nuclear safety R and D program. Important factors and regulatory issues for the safety analyses employing the advanced safety features are discussed and considerations for developing regulatory guide are presented herein. The safety and regulatory issues were discussed for the advanced safety features of the APR+ standard design and regulatory guide development strategy for new safety design features was proposed. The N₂ gas entrainment at the low discharge flow conditions of the SIT with FD+ should be further investigated for its cause and effects on the SI discharge flow. The regulatory safety evaluation should address the following safety issues related to the new safety design features of the APR+, (1) The effect of N₂ gas entrainment on the SI discharge flow at low flow conditions during SIT/FD discharge (2) The effect of ECBD on the normal plant operation and non-LOCA safety analyses as well as on the ECC bypass during LOCA. (3) PAFS and its non-safety components should be reviewed for their performance and the nonsafety system failures should be considered in the safety analyses. Safe shutdown and long term cooling requirements using PAFS should be developed as regulatory guides and its acceptance criteria should be confirmed by the startup tests as well as the safety analyses